Accessory Structures in Trenton, NJ (2026)
4 verified accessory structures rules for Trenton, New Jersey, sourced directly from the municipal code and official government pages.
Verified from official government sources
ADU Rules
Trenton allows one accessory dwelling unit per single-family lot under City Code § 315-9.4.B, capped at 800 square feet and 40% of the primary dwelling's floor area. The lot must be at least 4,000 square feet, and a detached ADU needs a 3-foot side setback and a 10-foot rear setback, with no added parking required.
Trenton ADU Zoning Standards
Some RestrictionsTrenton Code § 315-9.4.B(1), (3)-(8), (10)
1. An ADU may be located only on a lot with one single-family dwelling. ... 3. A lot must have a minimum area of 4,000 square feet to qualify for an ADU. 4. Only one ADU is permitted per lot. 5. The ADU may be within, attached to, or detached from the primary dwelling structure and may be a part of a detached accessory structure. An ADU may be developed within an existing structure or as new de...
ADU Owner Occupancy
Trenton requires that whenever a property has an accessory dwelling unit, the owner must live in one of the two units on-site. City Code § 315-9.4.B(2) states that 'one of the dwelling units must be occupied by the owner of the property,' closing off ADUs as a pure rental-only investment separate from an owner-occupant.
Trenton ADU Owner Occupancy Rule
Significant RestrictionsTrenton Code § 315-9.4.B(2)
1. An ADU may be located only on a lot with one single-family dwelling. 2. One of the dwelling units must be occupied by the owner of the property. 3. A lot must have a minimum area of 4,000 square feet to qualify for an ADU. 4. Only one ADU is permitted per lot.
Shed & Carport Rules
A shed in Trenton is a detached accessory structure, capped at 20 feet in height, and must be set back at least three feet from any lot line (one foot if enclosed and abutting an alley). Its footprint can't exceed the principal building's, and a building or zoning permit is generally required.
Trenton Shed Height, Setback and Permit Rules
Some RestrictionsTrenton Code § 315-9.4.A
General Regulations for Accessory Structures. All accessory structures are subject to the following regulations, unless otherwise permitted or restricted by specific regulations of this section and Ordinance. The maximum height of any detached accessory structure is 20 feet, unless otherwise permitted or restricted by this Ordinance. Setbacks for detached accessory structures are required as fo...
Garage Conversions
Trenton bars finishing the space above a detached garage's parking area into livable space with a kitchen or full bathroom unless it is approved as an accessory dwelling unit. City Code § 315-9.4.J(5) lets that same space serve as storage or a bonus room, but a cooking facility or full bath triggers the full ADU standards in § 315-9.4.B.
Trenton Detached Garage Conversion Rule
Significant RestrictionsTrenton Code § 315-9.4.J(5)
5. The area above vehicle parking spaces in a detached garage may not contain a cooking facility or a full bath. This does not apply if an accessory dwelling unit use has been approved, in which case those standards control.
Looking for Mercer County county-wide rules?
County ordinances apply to unincorporated areas and may supplement Trenton city rules.
Accessory Structures in Mercer County →